The long term objective of these studies is to understand where in the brain permanent memory representations are located and how they become established. The hippocampal system (i.e., the hippocampus and the adjacent, anatomically related entorhinal and perirhinal cortices) has now been shown to be necessary for normal memory function, but only for a limited time. The fact that damage to the hippocampal system produces temporally-graded retrograde amnesia has led to the idea the hippocampal system participates in the initial establishment of a memory and then directs the gradual strengthening, or consolidation, of more permanent memory representations in neocortex that, with the passing of time, become independent of the hippocampal system. This proposal includes a series of experiments to study the interactions between the hippocampal system and neocortex as memories are being established and consolidated. These experiments build on behavioral and electrophysiological work on learning and memory done in Dr. Eichenbaum's laboratory over the last decade as well as on the applicant's own work on memory consolidation. First, we will simultaneously record the activity of multiple single units to characterize the representations mediating the learning of odor paired associates in the hippocampal system and in olfactory cortex in the rat. The second study will examine the effects of lesions of two components of the hippocampal system on the representations in olfactory cortex of new and previously learned odor paired associates. The third study will examine the time course of the consolidation of the cortical representations for odor paired associates.